1. Field of the Invention
This invention relates to a control circuit for a video camera by means of which a charge image of an object to be recorded is adapted to be produced, this image being at least partly erased when being read out for a generating a video output signal of the video camera. Moreover, this invention relates to a method for controlling a video camera, comprising the method steps of producing a charge image of an object to be recorded and of producing a video output signal by reading out the charge image which at least partly erases the charge image.
2. Description of Related Art
Video cameras having control circuits which periodically produce a charge image of an object to be recorded by means of an image converter, which may be designed as a vidicon tube, have been known for quite a long time. In such a known video camera, the charge image of the vidicon tube is periodically scanned for generating a video output signal. During such a scanning of the charge image of the vidicon tube, the charge image is at least partly erased. In the known video camera, the scanning of the charge image for generating the video output signal is controlled by means of vertical and horizontal synchronization signals which effect a reading out of the charge image in synchronization with vertical synchronization pulses and horizontal synchronization pulses, the time distance between two subsequent synchronization pulses determining the read-out repetition rate for the charge image depending on the television standard according to which said video camera operates.
Such a known video camera comprising a control circuit operates in an extremely satisfactory manner when light is continuously supplied from the object to be recorded to the video camera.
If, however, the known video camera for recording an object is used with a periodically varying or periodically interrupted light supply from the object to be recorded to the video camera, the image of a video reproducing apparatus, which is produced by means of the video output signal of the video camera, greatly flickers.
A case which is of importance in practice and in which such problems arise, results from the use of the video camera for generating a monitor signal or for producing a video tape used for future film cutting work in a motion-picture mirror-reflux film camera. In such a case, the video camera is arranged in an optical viewfinder path of the motion-picture mirror-reflex film camera, either to make possible the evaluation of the momentarily recorded image on one or a plurality of monitors to persons other than the cameraman, or, for the purpose of supporting future film cutting work, to produce a video recording which is parallel to the filmed scene on a video tape on which, if necessary, additional data are reported for the film cut. In this case, the periodic presence and absence of a light supply from the object to be recorded to the video camera is due to the fact that a movable mirror diaphragm, provided in the optical path of the motion-picture mirror-reflex film camera, periodically opens and diverts, respectively, the light path from the object to be recorded in an alternate manner towards the film to be exposed and towards the video camera arranged in the optical viewfinder path.